1. Field of the Invention
The invention relates generally to a wireless communications network, like a cellular network, and more particularly to a method and system for voice-over-internet-protocol (VoIP) transmission in the network.
2. Description of the Related Art
A cellular network is a wireless communications system made up of a number of cells, each served by a fixed transmitter, known as a cell site or base station. Each cell site in the network typically overlaps other cell sites. The most common form of cellular network is a mobile phone (cell phone) system. The base stations are connected to cellular telephone exchanges or “switches”, which in turn connect to the public telephone network or another switch of the cellular company.
The 3rd Generation Partnership Project (3GPP) is a worldwide consortium to create a specification for a globally applicable third generation (3G) mobile phone system. 3GPP's plans are currently in development under the title Long Term Evolution (LTE). The 3GPP LTE project is to improve the Universal Mobile Telecommunications System (UMTS) terrestrial radio access mobile phone standard to cope with future requirements. Goals of 3GPP LTE include improving efficiency, lowering costs, improving services, making use of new spectrum opportunities, and better integration with other open standards. The 3GPP LTE technical specification is described in a set of reference documents including 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical Channels and Modulation (Release 8), 3GPP TS 36.211 V0.4.0 (2007-02); and 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 (Release 8), 3GPP TS 36.300 V8.1.0 (2007-06). In 3GPP LTE (E-UTRA and E-UTRAN) terminology, a base station is called an “eNode-B” (eNB) and a mobile terminal or device is called a “user equipment” (UE).
The data transmitted over the wireless network is often categorized as either non-real-time (NRT) data or real-time (RT) data. Examples of NRT data include data transmitted during web browsing by a UE or text-messaging to a UE, while an example of RT data is voice communication between UEs. In 3GPP LTE, voice communication (RT data) is considered the most important application and will be carried as voice-over-internet-protocol (VoIP) transmissions.
A typical VoIP session has periodic small VoIP data packets at fixed intervals and periodic silence indication (SID) packets at fixed intervals. There are thus two distinct periods in VoIP transmission: talkspurt periods during which VoIP packets are transmitted, and silence periods during which SID packets are transmitted. There are certain aspects or features of VoIP that can be improved with knowledge of the transitions between talkspurt periods and silence periods.
What is needed is a method and system for reliably detecting the transition between a talkspurt period and a silence period (i.e., the start of a silence period) and/or the transition between a silence period and a talkspurt period (i.e., the end of a silence period) during VoIP sessions.